The article seems to imply that the advatage of a Magnetohydrodynamic rocket is lower launch costs, but someone seems to be missing the fact that the chief advantage of an MHD engine is high exhaust velocity. This means higher thurst per kilogram of fuel expended, but also much reduced acceleration, far too little to take off from the Earth's surface, let alone get to orbit. Really, a perfect surface to orbit vehicle would have a specific impulse of arounf 1000 seconds (compared to the Shuttle's 452 sec)...
The interface is kinda rough, but the calculations use coplanar, cicular planetary orbits to find a least-energy transfer orbit using Lambert's method and Battin's (the guy who wrote the Apollo Guidence Computer) continued fraction interation. Velocities are in km/s.
This "throatless" engine seems more useful for testing injectors than actually extracting impluse (propulsion). The narrow throat of engine followed by a expanding nozzle allows for the chamber pressure to be high (good) while the exhaust pressure is lower (also good). This site explains much this and in fact says, "If the pressure ratio (and thus expansion ratio) [like Carmak's design] is 1, then F = 0. The only thrust produced by such a nozzle is the pressure thrust, or Ftotal = (Pe-Pa)Ae. Such a nozzle, of course, would have no divergent portion, since A*/Ae=1, and would be a badly designed rocket nozzle!"
You still have to move the cold water up from however many hundreds of feet down, probably taking more energy than you can efficently extract from the temperature differential. I'm confused over the "hose pipe siphon" analogy: If I place a hose pipe in an above-ground pool, I can siphon water out because the net change in elevation is negative; if I move the end of the pipe above the lip of the pool, no water comes out. Oh, and the highest capilparly column you can have is about a metre...
So, goo idea for air conditioning, but not a practical source of energy...
The first that comes to mind is the Russian Kliper; similar idea with lifting body crew cabin and orbital module behind... Kliper
Of course, there are obvious comparisons to Lookheed's LS-200 "Starclipper" proposal of the 1960's: LS-200
But the best analog is probably Dyna-Soar, the USAF spaceplane of the 1960's: picture, site...
The Death of Dyna-Soar
Ah, distinctly I remember, it was early last December;
It was felt that very shortly, we would be employed no more;
Every day we feared the morrow; vainly we had sought to borrow;
Funds to budget us tomorrow, for our work on Dyna-Soar...
On the sleek and winged spacecraft we called Dyna-Soar...
Cancelled now, forever more.
From off the duct I pulled the shutter, when, whith many flirt and flutter,
Out there flew a stately raven, of the saintly days of yore;
Not the least obeisance made he; not a minute stopped or stayed he;
But with mien of Lord or Lady, perched beside my office door...
Upon a bust of Eugen Sänger, on the bookcase by the door...
Perched, and sat, and nothing more.
"Prophet !" said I, "Thing of evil !, tell me, agent of the devil,
Whether McNamara axed the program, or just cut us back some more ?
Will he make a presentation, to Congress for appropriation ?
Does he plan continuation, after Fiscal 64 ?
Is the funding in the budget ? Tell me, tell me, I implore..."
Quoth the Raven, "Never more".
Oh, the sleek and winged spacecraft we called Dyna-Soar,
Cancelled now, forever more.
Because the Atlas V and Delta IV EELV's (Evolved Expendible Launch Vehicle) put the old Titans to shame; they are are chaeper per kilo to LEO and can be clustered together to form a Saturn I-class LV....
Let's leave the unrelated political comments about NASA's priorities out of the newsposts. Besides, NASA has all but committed to a robotic servicing mission....
Basically, there are two types of laser rocketry, as defined by fuel: air-burning, as used by Dr. Leik Myrabo and has been seen on tv; and soild fuel (usally a dense metal) burning, as being developed by Dr. Andrew Pakhomov at the University of Alabama in Huntsville. The problem with the Myrabo method is that the laser is tuned be absorbed by the air, and thus is inefficent over long distances. Ablative laser propulsion doesn't have this problem. It is however still very much theoretical: I've seen their first fight model; it's 3/4 of a cm tall...
It's always been easier to get military funding (ever wonder why it was called (d)arpanet?); the real question is what the US has specialities it. These probably include space, aeronautical, naval, and optical technologies. Tech dosen't just mean computers, despite what/.'ers think;-)...
The US Space and Rocket Center actually has two Saturn V's; one is a the flight atricle in not terrible state (not more than KSC's was before they build the enclosure) and a test article that has been fully assembled and towers a hundred and some feet high, high enough that I can see it from my dorm window...
http://www.spacecamp.com/spacecamp/request?type= ar ticle&id=museumindex&view=ind
That's one thing that always intrigued me about both Asmov's Empire/Foundation series and the Dune books; how do you govern a vast interplanetary empire?
BTW, I might be wrong, but I think Stadholder is a Dutch term; William III (of Orange) was a stadholder...
Slashdot Mirror
That's right! Visual novels can be can be Sci-Fi pron, Fantasy porn, Adventure porn and Horror Fiction porn!
;)
Simon
Indiana wants meee...
w ithout-telling-my-parents; I-hope-I-won't-get-in-troubleeee...
;)
But I can't go back there...
'Cause I'm a minor-who-just-bought-a-metric-tonne-of-AO-games-
Simon
The article seems to imply that the advatage of a Magnetohydrodynamic rocket is lower launch costs, but someone seems to be missing the fact that the chief advantage of an MHD engine is high exhaust velocity. This means higher thurst per kilogram of fuel expended, but also much reduced acceleration, far too little to take off from the Earth's surface, let alone get to orbit. Really, a perfect surface to orbit vehicle would have a specific impulse of arounf 1000 seconds (compared to the Shuttle's 452 sec)...
/ future_propulsion.html
;)
That's why NASA's own MHD program, VASMIR, is designed for in-space propulsion: http://www.nasa.gov/vision/space/travelinginspace
Simon
http://wombat.ods.org/cgi-bin/lambert.pl?p1=Earth& p2=Mars&sd=0&tf=90
;)
The interface is kinda rough, but the calculations use coplanar, cicular planetary orbits to find a least-energy transfer orbit using Lambert's method and Battin's (the guy who wrote the Apollo Guidence Computer) continued fraction interation. Velocities are in km/s.
Simon
This "throatless" engine seems more useful for testing injectors than actually extracting impluse (propulsion). The narrow throat of engine followed by a expanding nozzle allows for the chamber pressure to be high (good) while the exhaust pressure is lower (also good). This site explains much this and in fact says, "If the pressure ratio (and thus expansion ratio) [like Carmak's design] is 1, then F = 0. The only thrust produced by such a nozzle is the pressure thrust, or Ftotal = (Pe-Pa)Ae. Such a nozzle, of course, would have no divergent portion, since A*/Ae=1, and would be a badly designed rocket nozzle!"
;)
Simon
I hear it's dolphin- (and Arthur Dent)-free...
;)
The glaciers in Africa are a bit much, though...
Simon
You still have to move the cold water up from however many hundreds of feet down, probably taking more energy than you can efficently extract from the temperature differential. I'm confused over the "hose pipe siphon" analogy: If I place a hose pipe in an above-ground pool, I can siphon water out because the net change in elevation is negative; if I move the end of the pipe above the lip of the pool, no water comes out. Oh, and the highest capilparly column you can have is about a metre...
;)
So, goo idea for air conditioning, but not a practical source of energy...
Simon
Of course, there are obvious comparisons to Lookheed's LS-200 "Starclipper" proposal of the 1960's: LS-200
But the best analog is probably Dyna-Soar, the USAF spaceplane of the 1960's: picture, site...
The Death of Dyna-Soar
Ah, distinctly I remember, it was early last December;
It was felt that very shortly, we would be employed no more;
Every day we feared the morrow; vainly we had sought to borrow;
Funds to budget us tomorrow, for our work on Dyna-Soar...
On the sleek and winged spacecraft we called Dyna-Soar...
Cancelled now, forever more.
From off the duct I pulled the shutter, when, whith many flirt and flutter,
Out there flew a stately raven, of the saintly days of yore;
Not the least obeisance made he; not a minute stopped or stayed he;
But with mien of Lord or Lady, perched beside my office door...
Upon a bust of Eugen Sänger, on the bookcase by the door...
Perched, and sat, and nothing more.
"Prophet !" said I, "Thing of evil !, tell me, agent of the devil,
Whether McNamara axed the program, or just cut us back some more ?
Will he make a presentation, to Congress for appropriation ?
Does he plan continuation, after Fiscal 64 ?
Is the funding in the budget ? Tell me, tell me, I implore..."
Quoth the Raven, "Never more".
Oh, the sleek and winged spacecraft we called Dyna-Soar,
Cancelled now, forever more.
(hopefully not a future statement of the CEV!)
Simon ;)
Because the Atlas V and Delta IV EELV's (Evolved Expendible Launch Vehicle) put the old Titans to shame; they are are chaeper per kilo to LEO and can be clustered together to form a Saturn I-class LV....
;)
Simon
Let's leave the unrelated political comments about NASA's priorities out of the newsposts. Besides, NASA has all but committed to a robotic servicing mission....
;)
Simon
Basically, there are two types of laser rocketry, as defined by fuel: air-burning, as used by Dr. Leik Myrabo and has been seen on tv; and soild fuel (usally a dense metal) burning, as being developed by Dr. Andrew Pakhomov at the University of Alabama in Huntsville. The problem with the Myrabo method is that the laser is tuned be absorbed by the air, and thus is inefficent over long distances. Ablative laser propulsion doesn't have this problem. It is however still very much theoretical: I've seen their first fight model; it's 3/4 of a cm tall...
;)
More info on Dr. Pakhomov: pakhomov.uah.edu
Simon
It's always been easier to get military funding (ever wonder why it was called (d)arpanet?); the real question is what the US has specialities it. These probably include space, aeronautical, naval, and optical technologies. Tech dosen't just mean computers, despite what /.'ers think ;-) ...
Simon
The US Space and Rocket Center actually has two Saturn V's; one is a the flight atricle in not terrible state (not more than KSC's was before they build the enclosure) and a test article that has been fully assembled and towers a hundred and some feet high, high enough that I can see it from my dorm window...
= ar ticle&id=museumindex&view=ind
;)
http://www.spacecamp.com/spacecamp/request?type
Simon
That's one thing that always intrigued me about both Asmov's Empire/Foundation series and the Dune books; how do you govern a vast interplanetary empire?
BTW, I might be wrong, but I think Stadholder is a Dutch term; William III (of Orange) was a stadholder...
Wow, this device is almost identicle to the pentium 266mx in a cardboard box next to me!
;)
How much did it cost me? $20....
Simon
You don't really need Nitrogen; CO2 is a nice inert gas and there's alot of it on Mars.
;)
Simon
I belive that your sig should be attributed to Voltare, not Beatrice Hall.
;)
Simon
Funny is their lack of knowlege.
Scary is that they might soon be working for your ISP.
Sad is that all that MS training will soon be moot.
look at the pic; it's got 2 wings of equal area
:.
it's a biplane
LOL!